Comparing date ranges

sql

date-functions

performance-optimization

best-practices

byAnton Shumikhin·Oct 8, 2024

Here's the espresso shot of the solution: To determine if two date ranges overlap in SQL, simply check if one range starts before the other ends and ends after the other starts.

SELECT *
FROM your_table
WHERE start_date < @range_end AND end_date > @range_start; -- Coffee is hot ☕

This magic incantation will return any records where the date ranges intersect.

Dealing with non-overlapping periods

Let's flip the script and find non-overlapping periods instead. One range starts after the other range ends or one range ends before the other starts.

SELECT *
FROM your_table
WHERE start_date > @range_end OR end_date < @range_start; -- Flip-flops are great, especially when flipping logic! 👣

Feeling confident? Let's test your negation skills. Use the NOT operator to exclude non-overlapping periods in a single query:

SELECT *
FROM your_table
WHERE NOT (start_date > @range_end OR end_date < @range_start); -- Not today, overlap.. Not today.

Inside the box: Containment checks

Ever wondered if one date range is totally living inside another? Here comes containment check where we find out if a date range completely contains the other. Have the reversal magic ready and bang:

SELECT *
FROM your_table
WHERE start_date <= @range_start AND end_date >= @range_end; -- Who's your parent, little range?

This query will find records where the stored date range neatly wraps the provided one!

Nailing the edge cases

Beware of the edge cases! Perfect matches or at-the-edge overlaps can mystify range comparisons. Luckily, we have inclusive or exclusive comparisons to our aid:

Inclusive: WHERE start_date <= @range_end AND end_date >= @range_start; -- Welcome, all dates on the line! 🚀
Exclusive: WHERE start_date < @range_end AND end_date > @range_start; -- Strictly no trespassing beyond the line. 🚧

Remember, exceptions are not fun at parties, they're even less fun in your applications. Test these cases ruthlessly!

Performance: Making it quick

Whenever you're dealing with a room full of data, performance is crucial. Light up your query life by indexing your date columns. And of course, keep your eyes open for full table scans, the notorious villains behind slow performance.

Making the most of SQL's time date functions

Feel like a wizard yet? There's more! SQL has a treasure chest of date functions. From adjusting for daylight saving to juggling time zones, these functions are your magic wand.

Stick to the SQL Rules

Consistency wins the race. Use ISO 8601 for international standard date and time notation. Also, remember to let your database handle date calculations and comparisons. It's more reliable, efficient, and earns you some well-deserved rest!

explain-codes / Sql / Comparing date ranges

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